Electric resistance apparatus



Patented Oct. 7, 1952 ELECTRIC RESISTANCE APPARATUS Henry Paul-Huhne, Great Missenden, England A Application September 1, 1950; Serial No. 182.676 In Great Britain July 6, 1949' This invention relates to potentiometers, rheostats and similar electric apparatus of the kind provided with a dielectric supporting structure comprising a base and. the-core or cores carrying the resistance element or elements mounted as a rigid unit so as to prevent displacement of the resistance element or elements by the expansion and contraction thereof under the influence of the varying thermal effects developed in the resistance element or elements during use.

Electric resistance apparatus of the kind referred to, particularly when engaged on heavy duty are apt to become seriously overheated as the ceramic or other dielectric supporting structure thereoftends to retain or prevent dissipation of the heat developed in the resistance ele ment or elements.

The object of the present invention is to improve the construction and design of electric resistance devices of the kind referred to, so that heat is automatically dissipated as it is developed during use of the resistance apparatus so as to prevent overheating thereof without impairing the efliciency, strength and reliability of the same.

According to this invention, the dielectric supporting structures of electric resistance apparatus of the kind referred to are formed or provided with ventilating passages and apertures arranged so as to allow air to freely pass and circulate through and over the external and internal surfaces of the dielectric supporting structure so as to dissipate the heat developed with suflicient rapidity during use to prevent overheating of the apparatus. I

The invention will be more clearly understood by wayof example from the following description of an electric potentiometer, reference being made to the accompanying drawings in which:

Figure 1 is a plan view of a potentiometer,

Figure 2 is a view of the underside of the potentiometer, and

Figure 3 is a section on the line III-III of Figure 1.

The base I2 is formed in one piece from porcelain and has a laterally extending flange l3 projecting from a cylindrical lower part I4. Centrally disposed on the cylindrical lower part I4 is a boss 5 having a central bore I 6 passing right through the base.

The underside of the base I2 is recessed at and three arcuate apertures |8 are formed in the base between the annular upper surface M of the cylindrical part M and the recess H. The boss I5 is also provided with an annular recess 3 Claims. (01. 201-548) v IS, a downwardly projecting tapered element 20 being thusformed, through which element ,the bore 7 l6 passes. I A rib 2| projects laterally from the boss i5. v

The upper surface of boss I 5 has a raised rim 22 surrounding the widened end of the bore l6 which has a part 23 of square section. A circular plate 24 having a central aperture and a finger 25 is secured on the upper surface of boss |5 around the rim 22 with the finger overlying the rib 2|. The plate 24 is held in position by a bolt 26 which passes through rib 26 into a hole 2! therein.

The porcelain core 28 is of arcuate shape and has secured thereto the resistance element 29 by means of a suitable vitreous enamel in known manner. The core carrying the resistance element is secured in contact with flange 3 and the external Wall of cylindrical part I4 by means of the vitreous enamel in known manner and the core projects considerably above the surface of the cylindrical part, thus forming an annular space 30 between the core 28 and the wall of the boss l5. The apertures |8 thus enable air to pass freely from the underside of the base to the space 30, The rib 2| separates the ends of the core 28 and prevents possible movement between the core 28 and base I2.

In the bore l'6 is mounted a sleeve 3| having a square section part 36 located in part 23 of the bore. A spindle 3| within the sleeve 36 carries a potentiometer wiper arm 20 in the known manner. One end of the wiper arm 20 contacts the resistance element 29 while the other contacts the surface of the metal plate 24. The ends of the resistance element 2| are connected to terminals 32, 33 while the finger 25 carries a third terminal 34 in known manner.

It will be seen that in the construction described air can flow freely past both sides of the arcuate resistance element and along the internal and external surfaces of the base structure. Efiicient cooling of the resistance element is thus effected and overheating is avoided.

I claim:

1. A dielectric supporting structure for electric resistance apparatus comprising a base and an arcuate resistance-carrying core mounted on said base with at least a part of said core upstanding from the upper surface of said base, said base having on the upper surface thereof a bored in tegral central portion for a spindle for a potentiometer brush, which central portion projects centrally through said core and forms an arcuate ventilating space, open to the air, between said upstanding part of said core and said central portion and extending substantially the whole length of said core and said base being provided with ventilating passages between the underface of said base and said space.

2. A dielectric supporting structure for electric resistance apparatus comprising a base having a substantially flat, annular marginal surface, and an arcuate resistance-carrying core mounted on said marginal surface with at least a part of said core upstanding from the base, a central boss integral with said base projecting centrally through said core and having a central bore for a spindle for a potentiometer brush, the upstanding part of said core and said boss forming therebetween an arcuate space open to the air extending substantially the whole length of said core and. said base being provided with ventilating passages between the underface of said base and said space, whereby air is permittedfreely to pass through said passages and along either side of said core.

3. A dielectric supporting structure for e1ectric resistance apparatus comprising a base having an integral raised central portion with a central bore therein for a spindle for a-potentiometer brush and an arcuate recess round said arcuate portion but spaced therefrom, an arcuate resistance-carrying core mounted in said recess and round said raised central portion with a part thereof projecting from the surface of said base and beyond said central portion, the upstanding part of said core and said central portion of said base forming therebetween an arcuate space open to the air, extending substantially the whole length of said core and said base having a plurality of recesse therein communicating between said space and the underface of said base, whereby air is permitted freely to pass through said passages and along either side of said core.

HENRY PAUL-HUHN E.

REFERENCES CITED The'following references are of record in the file of this patent:

FOREIGN PATENTS Number Country Date 261,191 Great Britain Nov. 18, 1926 614,268 Great Britain Aug. 8, 1946 

